Acid grade fluorspar (calcium fluoride) is generally obtained by means of a froth flotation procedure in which the fluorspar ore is ground and slurried with water, treated with flotation reagents and then submitted to a froth flotation procedure. The floated concentrate containing the calcium fluoride is recovered and may be submitted to further cleaner flotation steps. The tailings from the flotation procedure consist of silicates and carbonates which may be discarded or processed further for recovery of desirable products. A large volume of water is required in the process and, in the past, most fluorspar flotation operations did not recycle the water.
Fluorspar flotation is very sensitive to water quality since soluble salts may interfere with the flotation and reduce the grade and recovery of the product. Accordingly, only fresh and in many cases softened water is used in most fluorspar flotation operations. However, with increased concern for environmental contamination, it is desirable to recycle a large portion or possibly all of the process water used in such operations. In order to recycle the water, the tailings from the flotation procedure must be treated and clarified to minimize the build-up of slimes and interfering soluble compounds.
Various flocculating agents or coagulants such as aluminum sulfate and ferric chloride have been proposed for settling slimes in the tailings water from fluorspar flotation operations. However, since soluble salts build up in such water, they are usually unsuitable, either for recycle or discharge into the environment. Various organic polymers have been proposed as coagulants or flocculants for use in mineral processing and waste water treatment. For example, the use of polyacrylamides, polysaccharides, and flocculating glues is proposed in U.S. Pat. No. 3,138,550. High molecular weight ethylene oxide polymers were proposed by Manley, U.S. Pat. No. 3,141,816 as flocculants for removing fibers and other solid materials from waste water from paper making processes. Technical Service bulletins for POLYOX ethylene oxide polymers and JAGUAR C-13, a cationic guar derivative, recommend their use as flocculants in mineral processing.